1. Field of the Invention
The present invention relates to a method for detecting a level of contamination of a particle sensor, and a particle sensor that is suitable therefor, with the aid of which, for example, soot particles in an exhaust gas stream of a motor vehicle may be detected.
2. Description of Related Art
A resistive particle sensor is known from published German patent application document DE 10 2005 053 120 A1 which has two comb electrodes situated on an insulator material for generating an electrical field. The particle sensor is situated in an exhaust gas stream of a motor vehicle so that soot particles may accumulate between the two electrodes. After a given time (blind period), enough soot particles have accumulated so that a current, which may be detected using a measuring device, is able to flow between the two electrodes. The measuring signal which is obtainable from the measuring device is proportional to the accumulated soot particles subsequent to a nonlinear transition phase, so that the quantity of accumulated soot particles may be detected in this linear measuring range. To prevent complete fouling of the particle sensor, the particle sensor must be regenerated by heating it to a temperature which is high enough to burn off the accumulated soot particles. The particle sensor is then ready for operation, and after the blind period has elapsed the particle sensor is able to detect accumulated soot particles.
A disadvantage of this type of particle sensor is that ash particles, which do not burn off during the regeneration of the particle sensor, also accumulate on the particle sensor.
Such ash occurs, for example, when additives are used for diesel particle filter regeneration, so that not only soot particles but also iron oxide and cerium oxide particles may accumulate in the particle sensor. The accumulated ash particles impair the accuracy of the particle sensor, so that such ash accumulations are therefore also referred to as “contamination” of the particle sensor.